I'm in the process of replacing my old radiator on my saturn 2000 sl1 since it is leaking very bad and already got a replacement but realize the copper tube where the transmission fluid goes in to the radiator to be cool is different from the upper and lower hole and i cant figure out how to disconnect that part from the old radiator and hope somebody might have some info on how to do it.. please help

 

That is a threaded fitting. The bottom one usually develops a lot of rust making it difficult to remove. Sometimes it is easier to take the line loose at the transmission and set it and the radiator on the bench where it will be more accessible.